As the longest-serving Democrat now in the Senate, Leahy moves to third place in the line of presidential succession, behind Vice President Joe Biden and House Speaker John Boehner

Biden swore Leahy in Tuesday as the successor to Hawaii Sen. Daniel Inouye in the Senate post. Inouye, who also chaired the Senate Appropriations Committee, died Monday at age 88. A vase of white roses was on Inouye's desk on the Senate floor.

Leahy also is in line to succeed Inouye as chairman of the appropriations panel. The 72-year-old Leahy currently is chairman of the Senate Judiciary Committee.